Motoko Komaki

Influence of detergent builders on surface properties of sodium dodecyl sulfate solutions under dynamic and static conditions

The effects of various detergent builders on surface properties of sodium dodecyl sulfate (SDS) solutions have been investigated by measuring the equilibrium surface tension and hysteresis curves of surface pressure vs surface area under dynamic conditions. While the adsorbed layer of SDS under static conditions is in the liquid-expanded state, a two-dimensional phase transition of the adsorbed layer from liquid-expanded to condensed-film can be observed on compression at higher rates beyond the saturated adsorption. For the SDS solution containing excess NaCl (1×10−1 M), the adsorbed layer of SDS is already in the condensed state under static condition due to a depression in the dissociation of SDS.It has been found that some polyelectrolytes, as well as conventional ionic builders, contribute to increasing the surface excess concentration of SDS together with promoting micelle formation and also to stabilizing the adsorbed layer of SDS. On the other hand, poly(vinyl alcohol) (PVA) as a nonionic polymer is adsorbed at the air-water interface in preference to SDS. In this case, the hysteresis of the dynamic surface behavior of the mixed solution can be attributed to the structural change of the adsorbed layer of PVA rather than SDS, which is different from the other ionic builders.

APPLYING DIFFERENTIAL SCANNING CALORIMETRY TO DETERGENCY STUDIES OF OILY SOIL

Differential scanning calorimetry (DSC) has been applied to studies of oily soil removal from fibrous materials. Fabric and filter paper were soiled with various oily substances present in sebum. After washing, the fibrous samples were subjected to DSC measurements. The residual oily soils on the samples were analyzed by the melting peak areas of the DSC heating curves, a method that is widely applicable to various oily substances with different melting points and polymorphic forms. Various woven or nonwoven fibrous samples can be scanned, regardless of sample size in washing experiments.

Formation of a liquid crystalline phase between aqueous surfactant solutions and oily substances

The process in which a ternary liquid crystalline (LC) phase containing surfactant, water and oily substance is formed after contact of aqueous surfactant solution and oily substance was investigated by a combination of (i) microscopic observation in polarized light and (ii) penetration of water-soluble or oil-soluble dye into LC phase. The structure of LC phase and the process of its formation were found to be affected by many factors, such as kinds of surfactant, surfactant concentration, alkyl chain length of oil and so on.Oil is supposed to be gradually incorporated into LC phase with time. The fact that parts of LC phase are projected into the exterior surfactant solution, and that the continuous phase within LC phase is water, suggest the possibility of the dispersion of LC phase into the exterior solution.The process of the formation of LC phase implies some contribution to oily dirt removal.The process of the formation of LC phase implies some contribution to oily dirt removal.

PHOTOFADING BEHAVIOR OF TRIAZINYLAMINOSTILBENE FLUORESCENT BRIGHTENER IN CELLOPHANE

The photofading behavior of CI Fluorescent Brightener 85 (FB 85) is investigated on cellophane. The initial photofading reaction of FB 85 on cellophane is trans-cis isomerization, and the subsequent reaction is assumed to be photodegradation. The initial photofading rate of FB 85 on cellophane is accelerated by brightener concen tration and atmospheric moisture, whereas the addition of sodium carbonate to the dyebath retards photofading. A kinetic analysis suggests the participation of a bimo lecular reaction in addition to photoisomerization through a monomolecular reaction. The contribution of the bimolecular reaction increases as the moisture content in creases. Added salt reduces the contribution of the bimolecular reaction in photofading of FB 85 on cellophane.

Effect of Zeolite on the Dispersion Stability of Particles

The effect of zeolite on the dispersion stability of particulate soils was investigated by absorbance and electrokinetic measurements. Ferric oxide and polystyrene latex particles were used for models of particulate soils. Maximum interaction potentials were calculated for the various interacting pairs of these particles, with surface potentials taken as the ζ-potentials found experimentally, and they provided reasonably high barriers against flocculation at low ionic strength (5 X 10-3 M). Experimentally ob served dispersion stabilities were in general accordance with this prediction. At high zeolite concentrations, however, a tendency against flocculation occurred for polysty rene-zeolite suspensions; zeolite slightly increases the dispersibility of coagulated poly styrene particles.

Effect of Zeolite on the Dispersion Stability of Iron Oxide Particles

The mechanisms of zeolite that contribute to the dispersion stability of iron oxide were investigated. It was evident that an interaction exists between iron oxide and zeolite by the sedimentation method and absorbance measurements. Moreover, zeolite enhances the dispersion stability of iron oxide particles. This study proves that zeolite exerts an effect of increasing pH, which is one of the mechanisms that contributes to the dispersion stability of iron oxide particles.